1. Field of the Invention
This invention relates to a method of processing vegetable protein and other ingredients optionally adding meat or meat by-products to produce intermediate moisture foodstuffs which simulate animal meat products in appearance, flavor, texture and taste. This invention also relates to a method comprising a series of extrusion cooking steps for producing the intermediate moisture foodstuffs described herein. These vegetable or vegetable/meat foodstuffs have prolonged shelf lives which make them suitable for human consumption that may be sold as a snack or high protein supplement without need for refrigeration.
2. Description of the Background
Animal protein is generally less abundant and more expensive than vegetable protein. It has been estimated that ten pounds of vegetable protein feed are required to feed the animal source for every pound of animal protein produced. It, therefore, makes economic sense to utilize vegetable rather than animal protein for the commercial preparation of foodstuffs.
Animal protein is prized for its flavor and its desirable nutritional balance of dietary essential amino acids. Its utilization, however, has disadvantages such as the fact that it is more expensive and generally less abundant than vegetable protein. It is thus desirable to substitute vegetable for animal protein whenever possible or to at least "extend" the use of animal protein by mixing in vegetable protein components and other ingredients. Examples of a vegetable protein source are soy and other oilseeds proteins, which are used in this invention to produce a meat-like texture product. Moreover, animal protein becomes denatured at approximately 170.degree.-180.degree. F. and cannot be reshaped at the higher temperatures which are needed to pasteurize microorganisms, whereas, such temperatures and higher may be used on the vegetable protein sources. In addition, the incorporation of vegetable protein influences the shelf life of an edible product.
Recent trends in food consumption also show that people are becoming more health conscious and monitoring their food intake as the result of recent research into the possible effects of particular foodstuffs on health. Animal products are the only dietary source of cholesterol and may contain high levels of saturated fats. This has led large numbers of health professionals to recommend that the public significantly reduce their intake of red meats Fish and poultry have become popular substitutes, but vegetable protein also is increasing in popularity. Generally, vegetable protein is eaten in the form of beans or other natural products alone or mixed with animal foodstuffs, but enriched sources such as flours, concentrates and isolates of defatted oilseed, especially soy, have been developed for use as food ingredients.
The term "intermediate moisture food", as used in the present patent defines a food that is flexible, easy to masticate, and does not produce dryness to the mouth while at the same time being resistant to microbial growth. In general, the foodstuffs falling under this category have a water content of about 15 to 40 wt %, and more preferably about 20 to 30 wt %.
Techniques for extending meat, meat by-products and/or trimmings with vegetable protein are known in the art.
U.S. Pat. No. 3,745,021 to Van Middlesworth et al. describes a method of making intermediate moisture pet foods using an extrusion/expansion technique. Meat trimmings are combined with 6-12 wt % water and a 3-25 wt % farinaceous material containing almost equal parts of wheat gluten/soy flour and starchy materials to produce a bubbly-textured non-fibrous end-product. Starchy materials disclosed are corn, wheat, barley and derivatives thereof. Intermediate moisture products are said to be achieved with water-soluble sugars that are added to the final product to raise its osmotic pressure. The high osmotic pressure created by the sugar is said to limit the amount of unbound water available to support microbiological growth.
U.S. Pat. No. 4,358,468 to Dolan et al. discloses a method of co-extruding vegetable proteins simulating red-meat and white-fat phases in an extruder to produce a pet food which resembles lean meat marbled with fat. Intermediate moisture levels are achieved in the above product with unspecified aqueous solutes. This prior art process casts and commingles homogenous red and white melts and results in a non-structured marbled product. It does not, however, produce entirely or partially striated fractions that resemble meat.
The above-described methods are primarily directed at making intermediate moisture foods for domestic pets that resemble the appearance of meat without actually having the various characteristics of meat.
A principal problem preventing long-term storage of ready-to-eat foodstuffs is the growth of microorganisms in a medium rich in nutrients. The growth of microorganisms, especially bacteria, is closely associated with the availability of free water in the foodstuff. The water available to microorganisms in a food product may be defined as the equilibrium relative humidity of the product rather than the weight percentage of water of the product. Yeast and molds, for example, are particularly effective in obtaining water even under lower water activity conditions than for bacteria. It is therefore of extreme importance for the successful production of a ready-to-eat product to significantly reduce the growth of microorganisms so that the foodstuff is shelf stable and can be stored for prolonged periods of time for retail sale.
Up to the present time, it has been a general practice to include additional food-grade chemical preservatives to prevent the growth of microorganisms in intermediate moisture foodstuffs.
An alternative method to retard microbial growth is the reduction of available moisture in the product. One method of achieving almost complete reduction of moisture is by dehydration. Dehydrated foods, however, have poor taste and texture, and must be rehydrated prior to consumption to make them palatable. It is, therefore, highly desirable that the processed food product have sufficient moisture to be palatable while keeping the microbial count low to prevent spoilage.
Thus, there still exists a need for a vegetable food product that resembles meat, is shelf stable and has an agreeable texture and feel to the mouth.